Cl804
Civil/Environmental
- Dec 19, 2017
- 2
Hello,
Just wondering if anyone here has ever had any issues with a Zwick/ToniTechnik extensometer for concrete cylinders and prisms? The instrument in question employs a pair of opposing transducers with lever-arm knife-edge supports. Strain is measured by the compression machine controller across the chosen gauge length.
I'm using one to determine Young's Modulus for 150mm diameter concrete cylinders to EN12390-13. Unfortunately, however, the instrument and associated controller have provided hugely-understated results for E when compared to theoretical projections (from Eurocode 2 and Model Code 2010). I have also attached resistive strain gauges to a number of cylinders in tandem with the extensometer. The strain gauge-derived values correlate perfectly with the theoretical values for Young's Modulus. Values given by the extensometer are approximately 25% smaller.
The test machine and extensometer have both been calibrated recently and are used solely by trained technicians. I have borrowed a second extensometer of the same model from a third party to test in my lab, and also tested both extensometers in another lab with another compression machine. Despite all of this, the results are consistently much lower than they should be.
Are these transducers just inherently poor and unfit for purpose? Do other researchers or engineers find that concrete extensometers provide E values close to those given by strain gauges?
Just wondering if anyone here has ever had any issues with a Zwick/ToniTechnik extensometer for concrete cylinders and prisms? The instrument in question employs a pair of opposing transducers with lever-arm knife-edge supports. Strain is measured by the compression machine controller across the chosen gauge length.
I'm using one to determine Young's Modulus for 150mm diameter concrete cylinders to EN12390-13. Unfortunately, however, the instrument and associated controller have provided hugely-understated results for E when compared to theoretical projections (from Eurocode 2 and Model Code 2010). I have also attached resistive strain gauges to a number of cylinders in tandem with the extensometer. The strain gauge-derived values correlate perfectly with the theoretical values for Young's Modulus. Values given by the extensometer are approximately 25% smaller.
The test machine and extensometer have both been calibrated recently and are used solely by trained technicians. I have borrowed a second extensometer of the same model from a third party to test in my lab, and also tested both extensometers in another lab with another compression machine. Despite all of this, the results are consistently much lower than they should be.
Are these transducers just inherently poor and unfit for purpose? Do other researchers or engineers find that concrete extensometers provide E values close to those given by strain gauges?
